Use of phi(glp-lac) in studies of respiratory regulation of the Escherichia coli anaerobic sn-glycerol-3-phosphate dehydrogenase genes (glpAB).

Expression of the glpA operon encoding the extrinsic membrane anaerobic sn-glycerol-3-phosphate dehydrogenase complex of Escherichia coli K-12 was studied in five strains carrying independent glpA-lac operon fusions. The location of the fusions was confirmed by transduction. Two of the strains produced an enzymatically active anaerobic sn-glycerol-3-phosphate dehydrogenase that accumulated in the cytoplasmic fraction of the cells. This suggests the loss of a specific membrane anchor subunit encoded by a distal gene, glpB, which was disrupted by the insertion. beta-Galactosidase in all five strains carrying phi(glpA-lac) was highly inducible by glycerol only anaerobically. A mutation in fnr, a pleiotropic activator gene, prevented full induction of the phi(glpA-lac), demonstrating that the Fnr protein is a positive regulator of the primary dehydrogenase as well as of the terminal reductases of anaerobic respiratory chains. Low concentrations of the respiratory poison KCN had a permissive effect on aerobic expression of phi(glpA-lac). Aerobic expression of the hybrid operon was also enhanced in isogenic derivatives of the fusion strains deficient in protoporphyrin biosynthesis (hemA). Thus, heme proteins may play a role in mediating aerobic repression of the anaerobic respiratory chain.     

Clustering of genes for L-fucose dissimilation by Escherichia coli.

Aerobic and anaerobic L-fucose utilization by Escherichia coli involves an inducible trunk pathway mediated by a permease, an isomerase, a kinase, and an aldolase. Tn5 insertion mutants of a parental strain expressing this pathway constitutively were used to map the positions of the structural genes by transduction. Results from this and previous studies show that all of the structural genes of the L-fucose trunk pathway map between eno and argA at minute 60.2 of the chromosome.     

Chemicomechanical transduction performed by enzymes activated by polymers

Kinetic models for the mode of action of processive and non-processive DNA-helicases are detailed. Fluxes at the steady state are analyzed, and the random walk of the enzymes on the DNA is studied in connection with the rate constants of the chemical reactions involved in the transformation of substrate to products. Finally, the constants of the kinetic model for the processive helicase are related to the parameters of an analogous viscoelastic model.     

A calcium ionophore-inducible cellular promoter is highly active and has enhancerlike properties.

We examined the regulatory/promoter sequence of a calcium ionophore-inducible gene isolated from the rat genome. Whereas the promoter of this ubiquitously expressed gene is active under noninduced conditions, after induction by calcium ionophore A23187 this promoter is 10- to 25-fold more active than the simian virus 40 early promoter, as measured by chloramphenicol acetyltransferase activities. Within this regulatory/promoter region, we have identified a DNA fragment with enhancer-like properties immediately 5' to the TATA sequence. This 291-nucleotide fragment acts in cis to enhance expression of the neomycin phosphotransferase (neo) gene driven by the herpes simplex virus thymidine kinase promoter in an orientation-independent manner. In addition, this fragment can confer A23187 inducibility to the neo gene and effectively compete for positive regulatory factors involved in A23187 induction. Sequence analysis of this promoter reveals homology with viral core enhancer sequences, and the apparent organization of direct repeat domains is similar to those observed in viral enhancers.     

Tyrosyl kinase activity is inversely related to prostatic acid phosphatase activity in two human prostate carcinoma cell lines.

Alterations in prostatic acid phosphatase (PAcP), a phosphotyrosyl phosphatase, corresponded to changes in overall tyrosyl kinase activity. PAcP added to extracts of prostate carcinoma cells with a low endogenous level of PAcP activity and elevated tyrosyl kinase activity decreased the tyrosyl kinase activity. On the other hand, when PAcP activity was decreased by the addition of androgens to cells, there was a corresponding increase in tyrosyl kinase activity.     

Role of hypothalamic histaminergic systems in the regulation of vigilance states in cats

We have studied the effects of local injections of histaminergic and antihistaminic drugs on the sleep-waking cycle in the cat. Microinjections of alpha-fluoromethylhistidine (alpha-FMH), a specific inhibitor of histidine decarboxylase, in the ventrolateral posterior hypothalamus, where histamine-immunoreactive neurons have been recently identified, resulted in a significant decrease in wakefulness (W) and increase in deep slow wave sleep (SWS). On the other hand, microinjections of SKF-91488 (Homodimaprit), a specific inhibitor of histamine-N-methyltransferase, increased W and decreased SWS and paradoxical sleep (PS). Microinjections of histamine also produced an increase of W, while this effect was abolished by pretreatment with mepyramine, an H1-histamine receptor antagonist.     

Amino acid sequence of bovine white matter proteolipid

The sequence of the bovine white matter proteolipid has been studied by a combination of proteolytic digestion and chemical cleavage at tryptophan residues. Alignment of peptides obtained by digestion with trypsin, chymotrypsin, clostripain, and Staphylococcus aureus protease gave the sequence of 52 residues at the amino terminus, 96 residues at the carboxyl terminus, and several additional segments. Peptides obtained by treatment of the protein with 2-(2-nitrophenylsulfenyl)-3-methyl-3'-bromoindolenine confirmed the alignment and extended the sequence. This information, combined with that of other investigators, permits us to propose the primary structure for the entire protein. On the basis of the sequence determination, the molecular weight of the proteolipid protein is 29,869.     

Regulation of cardiac contractile proteins by phosphorylation

Several of the contractile proteins of the heart can be phosphorylated, but in studies with isolated proteins only phosphorylation of the inhibitory subunit of troponin (TnI) produces a major change in the properties of the contractile system. As TnI is phosphorylated, the concentration of calcium required for activation of contraction is increased. Phosphorylation of the tropomyosin-binding subunit of troponin (TnT) or of the light chain of myosin fails to change ATPase activity of the isolated protein system. Phosphorylation of TnI is stimulated by the beta-adrenergic system and inhibited by the cholinergic system. Maximum calcium-activated force produced by the contractile system can be increased in hyperpermeable cardiac cells by cyclic AmP (cAMP) or agents that stimulate cAMP synthesis. This change in the contractile system, which appears to be part of the physiological response to beta-adrenergic stimulation, is mediated by phosphorylation of an intermediate that then modifies the contractile system. Phosphorylation of the contractile proteins is not involved.     

Enhanced Mineral Uptake by Zea mays and Sorghum bicolor Roots Inoculated with Azospirillum brasilense

Inoculation of corn (Zea mays) seeds with Azospirillum brasilense strain Cd or Sp 7 significantly enhanced (30 to 50% over controls) the uptake of NO₃⁻, K⁺, and H₂PO₄⁻ into 3- to 4-day- and 2-week-old root segments. No gross changes in root morphology were observed; altered cell arrangement in the outer four or five layers of the cortex was seen in photomicrographs of cross sections of inoculated corn roots. The surface activity involved in ion uptake probably increased, as shown by the darker staining by methylene blue of the affected area. Shoot dry weight increased 20 to 30% in inoculated plants after 3 weeks, presumably by enhancement of mineral uptake. Corn and sorghum plants grown to maturity on limiting nutrients in the greenhouse showed improved growth from inoculation approaching that of plants grown on normal nutrient concentrations. Enhanced ion uptake may be a significant factor in the crop yield enhancement reported for Azospirillum inoculation.     

Epidermis effects on spectral properties of leaves of four herbaceous species

The spectral properties of the leaves of the herbaceous species Brassica oleracea L. var. botrytis L., Cerastum tomentosum L., Petunia hybrida Vilm., and Talinum paniculatum (Jacq.) Gaertn. were examined to see what effect the epidermis had on leaf absorptance, reflectance and transmittance. Removal of the epidermis from the side of the leaf surface being illuminated resulted in increases in leaf absorptance and transmittance, and a decrease in reflectance in the 400–800 nm waveband. Removal of the epidermis from the opposite side of an illuminated leaf (effect was similar in both abaxial and adaxial surfaces) resulted in small decreases in both absorptance and reflectance, and corresponding increases in transmittance. Removal of both the upper and lower epidermis resulted in a marked increase in transmittance, while both leaf reflectance and absorptance were decreased. The results suggest that the presence of the epidermis significantly increases leaf absorptance in the photosynthetic wavebands.